Large lightweight mirrors are critical components in ground-based, airborne and outer-space-based imaging applications. Traditional mirrors intended for use in outer space drive the full system schedule requiring high cycle times and costs. While there are opportunities to reduce the cost and schedule in the manufacture of lightweight core, open- and closed-back mirrors, typically only nominal advances have been previously enabled.
Present methods of manufacturing a mirror for large telescopes involve reducing the weight of mirror by traditional abrasive water jetting (AWJ) or precision machining of a large boule, in which almost 95% material is eventually discarded. Such processing can take up to 2 years from ordering the glass boules to finishing. Due to these long cycle times, completed optical systems can take 3-4 years to manufacture. Corning's ULE® is commonly used for telescope mirrors.
Advanced ceramics and carbon composite materials have been offered as cost- and schedule-reducing alternatives to Corning ULE®, due to the high stiffness at relatively low mass and thermal expansion of these materials. However, mirrors based on carbon composite have issues with long term stability, and can suffer from deterioration based on thermal and hygro absorption. Fabrication of a composite core also requires precise layering of the carbon fiber prepreg, orientation, autoclaving and significant machining.
Current processes for producing mirrors do not allow for the rapid and low cost deployment of precision imaging capabilities.